This invention relates to four-cycle rotary engines and methods of operating same and more particularly to a method and structure for firing such engines.
There is a continuing interest in finding practical alternatives to the standard reciprocating internal combustion engine with much of this interest being focused on rotary engine research and development. Numerous types of rotary engines have been proposed including engines which do not utilize the conventional cylinder/piston construction, such as the well known Wankel engine, as well as engines which utilize a cylinder/piston construction but in an unconventional way, such as the engine disclosed in A. Z. Richards, Jr., U.S. Pat. No. 2,683,422. The latter type engine includes a cylinder unit or block having a plurality of cylinders radially arranged about an axis about which the block rotates. Pistons are disposed to move in the cylinders and also to rotate about a second axis offset and generally parallel with the first mentioned axis.
In a two-cycle Richards-type engine, the firing order would be predetermined by the nature of the operation, i.e., those cylinders to be fired would be fired in succession with every revolution of the cylinder block. In a four-cycle Richards-type engine, on the other hand, the cylinders to be fired would be fired on every other revolution of the cylinder block; thus a variety of firing orders are at least theoretically possible in the four-cycle engine depending upon the number of cylinders in the engine. The most obvious firing order in the four-cycle engine, and the one which can be employed in all such four-cycle engines regardless of the number of cylinders, is one in which all of the cylinders are fired in sequence during one revolution of the cylinder unit, then none of the cylinders are fired during the next revolution, etc. This is the firing order suggested in the aforecited Richards patent.
Since the firing order of the cylinders in any type engine employing cylinders and moving pistons affects the smoothness of operation of the engine as well as the amount of power developed, determination of the firing order is of critical importance. For example, the firing of each cylinder in sequence during one revolution and then the exhaustion of combustion products during the next revolution, etc., as described above, would result generally in an uneven, irregular power development especially at low r.p.m.